ws

1. Commercial in Confidence
2006-02-22
1 Telcel Optimization Workshop
Capacity
Some considerations
Mansour Akbari
Senior RF Consultant
GSDC, Sweden

2. Commercial in Confidence
2006-02-22
2 Telcel Optimization Workshop
Capacity overview
 System capacity performance tuning starts already in
the Radio Network Design Phase
 System will be able to accomodate more users if:
– Radio Network Design is based on solid grounds
– Does not suffer from interference (and properly Tuned)
– Does not have inconsistent settings (also Common
Channel powers), missing neighbours
– SHO areas are optimized
– Second Carrier is implemented
 System will accommodate more users if power usage
is optimized
 Ericsson UMTS system has features to Manage
Capacity
 Trade off approach

3. Commercial in Confidence
2006-02-22
3 Telcel Optimization Workshop
Soft HandOver Area
Too large overlaps in SHO area will cause capacity
reduction

4. Commercial in Confidence
2006-02-22
4 Telcel Optimization Workshop
SHO and System Capacity (1)
- Trade-off between Soft/Softer Handover and system
capacity.
- UE involved in Soft/Softer Handover uses several radio
links, more downlink channelization codes, and more
downlink power than a single-link connection.
-If all the UEs connected to a particular RNC are
considered, more resources are needed in the RBSs, more
resources over the Iub and Iur interfaces, and more
resources in the RNC.

5. Commercial in Confidence
2006-02-22
5 Telcel Optimization Workshop
SHO and System Capacity (2)
- Number of radio links involved in the Soft/Softer
handover must be limited.
- Radio network planning and optimization must
determine the size of the handover areas between the
cells.
- No. of neighbours should be limited to maximum 15-20

6. Commercial in Confidence
2006-02-22
6 Telcel Optimization Workshop
Number of Radio Links and Capacity
 Ericsson recommends AS of 3 as max (but it can be set up to 4).
Having more RL in AS can reduce capacity.
 It is possible to monitor average number of RLs in SHO by means
of counters
– We can change SHO borders
– Monitor counter values if we have achieved improvement
Soft/Softer Radio Link Count per Utran Cell

7. Commercial in Confidence
2006-02-22
7 Telcel Optimization Workshop
f2 R99
f1 R99+HSDPAf1 R99+HSDPAf1 R99+HSDPAf1 R99 f1 R99f1 R99+HSDPA
f2 R99+HSDPA
Second Carrier
The capacity can be increased by adding the second
frequency

8. Commercial in Confidence
2006-02-22
8 Telcel Optimization Workshop
UL noise rise / Missing neighbor/Capacity
 UL Noise rise limits capacity
 Missing neighbor will cause UE to be power controlled
by ”wrong” RBS
 UE Tx Power will increase, making also all others UE’s
to increase their UE Tx Power, so total UL Noise Rise
increases
 System will have reduced capacity

9. Commercial in Confidence
2006-02-22
9 Telcel Optimization Workshop
Trading Coverage for Capacity (1)
 Limit coverage for high rate users
– By reducing Dlmaxpower for PS384, users will use lower
bitrates to a higher extent
 Reducing output power of CCH
– Decreased coverage, changed SHO areas, increased
capacity

10. Commercial in Confidence
2006-02-22
10 Telcel Optimization Workshop
Trading Coverage for Capacity (2)
 Reducing CCH power
– Reduce power for primary CPICH by 1 dB
 7% gain

11. Commercial in Confidence
2006-02-22
11 Telcel Optimization Workshop
Trading quality for capacity
 Adjust admission threshold
– Difference between admission limit (pwrAdm) and maxpower
used for mobility
– Can use some of this headroom to serve more users
– Risk is higher rate of congestion

12. Commercial in Confidence
2006-02-22
12 Telcel Optimization Workshop
Trading quality for capacity (2)
 Decrease power per user
– Adjusting PS BLER targets, hence higher BLER, greater
delay on selected PS bearers
 Limit max allowed users per bearer
– Limit high rate users by lowering parameter sf8Adm.
– More lower bit rate users

13. Commercial in Confidence
2006-02-22
13 Telcel Optimization Workshop
System Capacity Management
Function
 Ericsson UMTS System has mechanism to
manage system capacity
– Dedicated Monitored Resource Handling
– Admission Control
– Congestion Control

14. Commercial in Confidence
2006-02-22
14 Telcel Optimization Workshop
Dedicated Monitored Resource Handling
 The Dedicated Monitored Resource Handling function
collects and provides information about the current
usage of resources that are critical to the load of the
cell.
 This is done by performing measurements and keeping
track of every radio link addition, deletion and RL
modification in the cell.

15. Commercial in Confidence
2006-02-22
15 Telcel Optimization Workshop
Admisssion Control (1)
 The Admission Control function accepts or refuses
requests for utilization of dedicated monitored
resources. Requests are initiated when new
connections are setup, existing connections are
modified, and when performing soft handover.
 To decide on the requests, the Admission Control
function requires information about the load on the
dedicated monitored resources and the amount of
resources needed by the requester. (This information is
provided by the Dedicated Monitored Resource
Handling function.)

16. Commercial in Confidence
2006-02-22
16 Telcel Optimization Workshop
Admission Control (2)
 Admission Control blocks or admits the radio link
requests according to admission policies defined on
requested dedicated monitored resources.
 Admission Control policies can differentiate
accessibility of dedicated monitored resources between
different service classes (guaranteed and non-
guaranteed) and setup types (handover and non-hand
over)
 Differentiation makes it possible to reserve dedicated
resources for guaranteed service class connections
and for mobility

17. Commercial in Confidence
2006-02-22
17 Telcel Optimization Workshop
Congestion Control (1)
 The Congestion Control function detects overload
situations on some of the dedicated monitored resources
and initiates congestion resolve actions to resolve this
overload.
 To detect overload, the function uses the Downlink
Transmitted Carrier Power and the uplink Received
Total Wideband Power (RTWP) measurements from the
Radio Base Station (RBS). When the downlink
transmitted carrier power exceeds a predefined limit, the
cell is considered to be downlink congested. When the
uplink RTWP exceeds a predefined limit, the cell is
considered to be uplink congested.
 The uplink congestion policy is currently deactivated

18. Commercial in Confidence
2006-02-22
18 Telcel Optimization Workshop
Congestion Control (2)
 When a cell is congested, Congestion Control orders
Admission Control to deny all radio link requests and
modifications that worsen the congestion situation.
 In case of downlink congestion, Congestion Control
additionally initiates congestion resolve actions to
decrease the load until the congestion situation
resolves ( e.g. release of Interactive PS connection).
 Congestion resolve actions aim to cause as little
negative impact as possible on the retainability of the
existing radio connections

19. Commercial in Confidence
2006-02-22
19 Telcel Optimization Workshop
Conclusion- How to improve capacity
 Capacity dimensioning has done properly
 Radio Network Design is based on solid grounds
 SHO areas are not two large (optimized)
 Not too many neighbours defined
 Radio network are properly tunned
 Power of CCHs are set accordingly (< 25% of total power)
 Radio network does not suffer from interference
 BLER Quality target is set properly (not below Ericsson
recommended values)
 Admission parameters are set properly
 Limit the number of 384 users
 Second Carrier where is needed

20. Commercial in Confidence
2006-02-22
20 Telcel Optimization Workshop